The present invention is related to a rotational speed switching apparatus of a ceiling fan. The switching apparatus has four contacts cooperating with only two voltage-dropping capacitors to achieve five-stage switch of the rotational speed.
FIG. 9 shows a conventional rotational speed switch of a ceiling fan. The rotational speed switch includes a pull rotary assembly 81 for driving a rotary shaft 83 disposed in a seat body 82 to one-way circularly rotate. A stepped conductive ring 84 is fitted around the rotary shaft 83. The interior of the seat body 82 is partitioned into four receptacles 821, 822, 823, 824 in which conductive leaf springs 85, 86 and conductive members (not shown) are respectively disposed to form four contacts L, A, B, C. Accordingly, an operator can pull and rotate the pull rotary assembly 81 to control the rotational speed of the ceiling fan.
FIG. 10 is a circuit diagram of the conventional rotational-speed switch of the ceiling fan. When the contact L is not in contact with other contacts, the motor of the ceiling fan is turned off. When the contact L is electrically connected with the contact A, via an activating capacitor 871, an activating coil 881 is energized to activate the motor. After the motor operates, directly through the forward backward switch 89, a main coil 882 is energized to drive the motor to operate at high speed. When the contact L is electrically connected with the contact B, the current will pass through a first capacitor 872 with lower capacitance and the forward backward switch 89 to energize the main coil 882 to drive the motor to operate at middle speed. When the contact L is electrically connected with the contact C, the current will pass through a second capacitor 873 with higher capacitance and the forward backward switch 89 to energize the main coil 882 to drive the motor to operate at low speed. Accordingly, the rotational speed can be switched among four stages, that is, stop, fast, middle and slow stages.
However, the four-stage switch of rotational speed is insufficient at present time. It is now commercially required to have five-stage switch of rotational speed. In case the conventional rotational speed switch is expanded to five-stage switch, the circuit will be more complicated and the number of capacitors will be increased. This will increase the manufacturing cost and lower the competitive ability of the product.